####空气质量查询###
i = 0
#创建无限循环
while i == 0 :
    pm2_5 = int(input("请输入pm2.5的值："))
    if 0<=pm2_5<=50:
        print("今天的空气质量是：优秀")
    elif 51<=pm2_5<=100:
        print("今天的空气质量是：良好")
    elif 101<=pm2_5<=150:
        print("今天的空气质量是：轻度污染")
    elif 151<=pm2_5<=200:
        print("今天的空气质量是：中度污染")
    elif 201<=pm2_5<=300:
        print("今天的空气质量是：重度污染")
    else :
        print("今天的空气质量手机：严重污染")
    #输入Q退出
    panduan = input("输入Q退出，输入任意值继续")
    if panduan == "Q" or panduan == "q":
        break